The present invention relates to an intermediate heat exchanger-incorporated type steam generator provided with an intermediate heating exchanger tube and a steam generating heat exchanger tube separately in the interior of a vessel, and having a function of generating steam by forcibly circulating a secondary coolant (intermediate coolant) in the vessel to thereby subject the coolant to heat exchange. This technique is especially useful for a steam generator in a liquid sodium-cooled reactor.
In a fast breeder reactor using liquid-metal sodium as a coolant, electric power is generated by a turbine, so that a steam generator adapted to generate steam with the heat of sodium is employed. This steam generator is generally constructed so that liquid sodium is passed through the interior of a heat exchanger tube and water around the heat exchanger tube is heated and turned into steam. However, sodium has the property of violently reacting with water. Therefore, a secondary cooling system using an intermediate heat exchanger and a secondary coolant of sodium is generally employed so as to prevent the influence of the interaction of water with sodium from being exerted on a reactor core in the unlikely event of the breakage of the heat exchanger tube in the steam generator. Namely, the reactor core is cooled with a primary coolant of sodium, and a secondary coolant of sodium is heated with the heat of the primary coolant sodium in the intermediate heat exchanger. The secondary coolant sodium is then guided into the steam generator, where water is heated with the heat of the secondary coolant sodium and turned into steam.
As compared with a structure in which steam is generated in a steam generator by directly using the primary coolant sodium which has passed through a reactor core, the above-described secondary cooling system is advantageous in that the influence exerted on the reactor core is little when the heat exchanger tube should be broken, and in that activated sodium does not leak out. On the other hand, there is required various kinds of equipment in the secondary cooling system including an intermediate heat exchanger, a primary pump, piping installation, auxiliary equipment such as measurement control equipment, preheating equipment, sodium purification equipment and the like, a dump tank and so on. Also, since a large quantity of secondary coolant sodium is necessary, the cost increases. Moreover, a large space in which these various kinds of equipment are installed is also needed.
An object of the present invention, therefore, is to provide an intermediate heat exchanger-incorporated type steam generator having both functions of an intermediate heat exchanger and a steam generator so that a secondary cooling system can be simplified and a quantity of sodium coolant and an installation space required for the secondary cooling system can be greatly reduced.
Another object of the present invention is to provide an intermediate heat exchanger-incorporated type steam generator capable of securing a high safety even in the unlikely event of the breakage of a heat exchanger tube.
According to the present invention, there is provided an intermediate heat exchanger-incorporated type steam generator comprising: a vessel storing a secondary coolant therein, an intermediate heat exchanger tube and a steam generating heat exchanger tube separately disposed in the vessel, and a pump mechanism for forcibly circulating the secondary coolant in the vessel.
According to the present invention, there is also provided an intermediate heat exchanger-incorporated type steam generator comprising: a cylindrical vessel storing a secondary coolant of liquid sodium therein, an inner cylinder disposed in the cylindrical vessel to form a flow passage of the secondary coolant and divide the flow passage into flow passage portions inside and outside the inner cylinder, a helical coil-shaped steam generating heat exchanger tube disposed in an upper portion of the interior of the inner cylinder, an intermediate heat exchanger tube disposed separately from the steam generating heat exchanger tube in a lower portion of the interior of the inner cylinder, and an electromagnetic pump mechanism formed by an electromagnetic driving coil provided on an outer circumference of the cylindrical vessel and a magnetic core attached to the inner cylinder. The secondary coolant is forcibly circulated in the vessel so that the secondary coolant flows upward in the flow passage portion inside the inner cylinder and flows downward in the flow passage portion outside the inner cylinder.
In the steam generator described above, it is possible to divide the flow passage portion between the cylindrical vessel and the inner cylinder into a plurality of parts by a plurality of radially disposed partition plates. In such a case, the electromagnetic driving coil is miniaturized and a plurality of miniaturized electromagnetic driving coils are provided on the outer circumference of the cylindrical vessel.
In the preferred embodiment of the present invention, at least one porous plate or slotted plate is disposed between the intermediate heat exchanger tube and the steam generating heat exchanger tube. Thereby, the influence of the breakage of one of these heat exchanger tubes is not exerted on the other. In the case where a plurality of porous plates or slotted plates are disposed, they should be positioned with a space between each other.